Inhlaled Anesth. Part 2 Add-On

Question 1

Most drugs will decrease MAC requirement with the exception of:

Answer 1

Acute amphetamine, cocaine, ephedrine

Chronic ampthetamine use will decrease MAC

Question 2

_____% of patients should not move at 1.2 MAC.

Answer 2

95%

MAC has a standard deviation of ~ 10%

Question 3

T/F all the drugs at 1 MAC are equal, it just takes more drug to get to MAC.

Answer 3

True

Question 4

What is MAC awake?

Answer 4

• the minimum concentration where 50% of people respond to the command “open your eyes”
• this end tidal concentration is 1/3 MAC
• associated with loss of recall

Question 5

What is MAC bar?

Answer 5

MAC necessary to block adrenergic response to skin incision
~ 1.5 MAC
- changes in norepinephrine concentration: HR, MAP

Question 6

What is MAC intubation?

Answer 6

Similar to MAC bar

- it’s value exceeds the anesthetic requirement for skin incision

Question 7

MAC is additive. What restricts this?

Answer 7

Amount of time between doses of muscle relaxants—> pt won’t move, but it doesn’t mean they don’t want to

Question 8

What is elimination like with volatile anesthetics?

Answer 8

They are exhaled unchanged, or minimally metabolized by the liver

Question 9

What is the primary objective with inhaled anesthetics?

Answer 9

To obtain a constant and optimal partial pressure (Pbr) of anesthetic in the brain

• do this by controlling inspired partial pressure of gas
• the brain and all other tissues equillibrate with the partial pressure of anesthetic delivered to them by arterial blood

Question 10

Transfer from blood to brain depends on:

Answer 10

• brain:blood partition coefficient (1.7, 1.57, 1.39)
• cerebral blood flow
• arterial/venous partial pressure difference

Question 11

How does the rate of breathing (hyper vs hypoventilation) affect induction?

Answer 11

• hyperventilation increases induction
• hypoventilation slows induction
• spontaneous ventilation is always better —> pulls gas instead of you pushing it in

Question 12

What do you do if the surgeon is ready for incision, but the patient is not?

Answer 12

Turn up the concentration and flows to hurry up and get them where you want the to be
** RATE OF GAS FLOW IS VERY IMPORTANT **

Question 13

What are the implications of high blood solubility?

Answer 13

A large amount of anesthetic must be dissolved in blood before equilibrium with gas phase is reached

Question 14

What does high CO (fear) do for induction?

Answer 14

Slows induction (rate of rise is slower)
- blood moving so fast you can’t fill up all of the seats

Question 15

What does low CO (shock) do for induction?

Answer 15

Speeds up induction (speeds up rate of rise)

- blood moving slower, more time to fill up seats

Question 16

What will a right to left shunt do to the rate of induction and what is this called?

Answer 16

Slows rate of induction—> “dilutional effect”

Bypasses the lungs

Question 17

How many time constants are required for complete equilibration of any tissue, including the brain, with the Pa?
How long is this in minutes?

Answer 17

At least 3 time constants

6-12 min

Question 18

What does PA-PV reflect?

Answer 18

The tissue uptake of inhaled anesthetic

Question 19

After 3 time constants,how much of returning venous blood flow is at the Sam partial pressure as PA?

Answer 19

75%

- as end tidal concentrations increase we know tissues are getting more saturated with agent

Question 20

Emergence is the inverse of induction. What 3 factors play into this?

Answer 20

• alveolar ventilation—>use high FGF and hyperventilate to wash out gas
• solubility
• CO

Question 21

During emergence, there is a potential for “diffusion hypoxia”. What does this mean?

Answer 21

Happens when nitrous oxide is abruptly stopped, and pp in blood is higher than in alveoli
(Nitrous diffuses faster than oxygen)
When nitrous stopped, it diffuses rapidly into the alveoli, diluting O2 concentration—> hypoxia
* prevent this by giving 100% O2 for 5-10 minutes after N2O stopped *

Question 22

What are factors that influence the rates of emergence?

Answer 22

• duration of procedure—> how long gas was running
• temperature of patient: cooler pt=gas more soluble, slower emergence
• physical condition of patient—> not doing well will slow things down
• obesity: may initially wake up, bu then as agent is mobilized from fat stores they may re-anesthetize themsleves

Question 23

How much anesthetic must be eliminated for pt to regain coordinated functions?

Answer 23

All but a small amount to restore the ability to swallow and maintain effective respiratory effort